The invention relates in general to remote laser welding systems, with particular reference to the welding of motor vehicle bodies and respective components.
Currently known remote laser welding systems comprise a laser beam generator and an optical unit, consisting of a optical bench, comprising mirror orienting means and focusing means, to orient and focus the laser beam, respectively, inside a truncated pyramid.
Two solutions are generally provided to orient the laser beam inside the truncated pyramid in such remote laser welding systems of the known kind: in a first case, said orienting means comprise two mirrors pivoting on reciprocally perpendicular axes (for example, each laying on the surface of the respective mirror); in the second case, said orienting means comprise one only mirror pivoting on two reciprocally perpendicular axes (for example, both laying on the surface of the mirror itself). The oscillations of the mirrors are generally controlled by galvanometric systems.
In these known solutions, the spatial orientation of the truncated pyramid for focusing the beam and providing three dimensional welding (i.e. also on surfaces arranged on planes with are not only horizontal but which also lay on vertical or slanted planes) entails a number of technical difficulties, because either the entire optical bench or the part to be welded must be angularly moved. Alternatively, several optical benches must be used. In addition to constructive complexity and to problems related to fabrication, this entails redundancy of at least one movement, because the angular movement of the optical bench or optical benches or that of the part to be welded is performed on the same plane as one of the two oscillations of the mirror orienting means in known systems described above.
The object of this invention is to obviate this shortcoming and make a remote laser welding system of the type described above capable of three-dimensional welding without the need for an additional axis for moving the optical unit, consisting of an optical bench, while providing maximum precision and operating reliability.
According to the invention, this object is reached essentially by a remote laser welding comprising a laser beam generator and an optical unit including mirror orienting means and focusing means, to orient and focus the laser beam respectively inside a spatial sector, said optical unit consisting of an optical head and said orienting means being arranged to further orient said spatial sector on a vertical plane.
According to a preferred embodiment of the invention, the orienting means comprise a stationary mirror to deviate the laser beam from a vertical direction to a horizontal position, a mobile mirror pivoting on a first horizontal axis arranged on the plane of said mobile mirror orthogonally to said horizontal direction of the laser beam, and pivoting on a second horizontal axis coinciding with said horizontal direction of the laser beam, and high dynamic actuating means for controlling the angular movements of said mobile mirror with respect to said first and said second axis.
Practically, in the remote laser welding system according to the invention, the rotation of the mobile mirror on the second horizontal axis coinciding with the axis of the incoming laser beam generates the spatial sector, conveniently formed by a spherical crown sector, unlike the traditional truncated pyramid configuration, orienting it as required on a vertical plane at the same time. This provides a considerable simplification in relation to the spatial orientation of the spatial sector, because the need of an additional controlled movement axis of the entire optical unit or the part to be welded is avoided.
According to another aspect of the invention, said focusing means comprise a focusing lens vertically moveable upstream to said stationary mirror.
This solution advantageously avoids variations of the focused laser spot in the zone to be welded, whereby ensuring a considerable rapidity in focusing.
The laser welding system according to the invention is particularly suitable for being applied on Cartesian robots for welding bodies of motor vehicles. In such applications, the robot, e.g. of the gantry type, behaves as an optical head positioner, while the part being worked is fixed, and makes the process faster by continuously tracking the focused spot during all phases of welding because repositioning of the optical head is carried out at the same time as the welding. Thanks to the possibility of directing the focused laser beam inside the three-dimensionally adjustable spatial sector, the remote laser welding system according to the invention is capable of complex welding also along vertical surface or surfaces which are however spatially oriented.